Need help accessing a subdocument in a subdocument

Hello, I am working with Nodejs and Mongodb, particularly Mongoose.
I have THREE schemas. The main schema creates the username/pass and has an ‘events’ category. That Events category is itself a schema, and inside the events schema there is a Gift schema.
UserSchema, EventsSchema, GiftSchema.
Events & Gift Schemas are now technically subdocuments, since they are embedded in the main User Schema.
When I query (using a Mongoose.model Method), I can findById the UserSchema, and in the UserSchema I can push to the Events subdocument array to add new events. What I CAN NOT figure out how to do, is to push to the Gift subdocument array. I need to add multiple gifts to ONE event, and I cannot query and find a particular events ID so that I may do a PUT or POST operation.